(KSTU/CNN) — Doctors often say twins run in the family. It could not be more true when it comes to twin sisters from Utah.

Both of them just found out that they are pregnant with a second set of twins.

Kelli Wall broke the news to her sister Kerri Bunker over the phone that after going through in vitro fertilization, she was pregnant with not one, but two babies.

“That day, for whatever reason after Kelly told me she was having twins,” Bunker said, “I thought what if I`m pregnant?”

Four years earlier, Bunker was told she would not be able to get pregnant naturally and was advised by doctors to freeze embryos if she wanted more children. She did as they suggested and did not expect to get pregnant until she decided to use them.

“The fertility specialist said it would be nearly impossible,” she said — which is why she was so surprised when she got a positive result.

“It was such a shock to me and Kelli had just shared her amazing news, I immediately get on the phone with my husband,” Bunker said.”He doesn’t believe me and said ‘I’m coming home right now, we’re heading to the hospital for a blood draw.”

She said she had mixed emotions when it was confirmed she was pregnant with another set of twins. “I’m really nervous about the fact that there`s two more coming. I’m going to have five kids under the age of four and how am I going handle it?”

The sisters’ first set of twins are four-years-old. They say they say their families will be full after the new babies arrive. “If these babies get here nice and healthy, we are done,” said Bunker. “So am I,” added Wall.

This is not the first adventure Kelli and Kerri have been on together. They say they have been attached at the hip since they were born.

“We never took a separate class in college,” said Bunker. “We’ve done absolutely everything together and, really, she’s my best friend.”

“Every night before we go to bed at about 9:45, 10 o`clock, we call each other goodnight,” said Wall.

They even set rules for who they would marry. “Twins first, brothers or best friends, and we got our third choice,” Wall said, “so we still feel pretty good about it.”